\\[-1.8ex] Soil Heterogeneity & $-$2.955$^{***}$ & $-$2.773$^{***}$ & $-$2.788$^{***}$ & $-$2.326$^{***}$ \\ 
  & (0.799) & (0.792) & (0.723) & (0.686) \\ 
\\[-1.8ex] 
Observations & 23,437 & 23,437 & 23,153 & 23,153 \\ 
R$^{2}$ & 0.549 & 0.557 & 0.563 & 0.592 \\ 
